1. Field of the Invention
The present invention relates to a solid-state radiation detector constructed to receive radiation representing image information to record the image information therein, and to output image signals representing the recorded image information.
2. Description of the Related Art
Today, in radiological imaging for medical diagnosis, a variety of solid-state radiation detectors is proposed and put into practical use. Such detectors are constructed to tentatively store charges in a storage section of a solid-state detection element obtained by detecting radiation, and to output the stored charges after converting to image signals representing radiation image information. For example, from the aspect of charge generation process in which radiation is converted to charges, two types of solid-state radiation image detectors are proposed, one of which is called an optical conversion type and the other of which is called a direct conversion type. From the aspect of charge readout process in which stored charges are read out, two types of solid-state radiation image detectors are proposed, one of which is called a TFT (thin film transistor) readout type and the other of which is called an optical readout type.
Here, the optical conversion solid-state radiation detector includes, for example: a solid-state detection unit (image readout unit) including multitudes of photoelectric conversion elements (solid-state detection elements) formed in a matrix on an insulative substrate; and a phosphor stacked on the solid-state detection unit, thereby fluorescence emitted from the phosphor when radiation is irradiated thereon is detected by the photoelectric conversion elements, and signal charges obtained through the photoelectric conversion are tentatively stored in the storage sections of the photoelectric conversion elements (normally, in the case of optical conversion type, the photoelectric conversion section also serves as the storage section), then the stored signal charges are converted to image signals (electrical signals) and outputted, as described, for example, in Japanese Unexamined Patent Publication No. 2(1990)-164067.
The direct conversion solid-state radiation detector includes, for example, a solid-state detection unit including multitudes of charge collection electrodes formed in a matrix on an insulative substrate, and a radiation conductor, stacked on the charge collection electrodes, that receives radiation to generate charges representing radiation information, thereby signal charges generated in the radiation conductor when radiation is irradiated thereon are collected by the charge collection electrodes and tentatively stored in the storage sections, then the stored signal charges are converted to electrical signals and outputted as described, for example, in Japanese Unexamined Patent Publication No. 1(1989)-216290.
The TFT readout method is a method in which signal charges stored in the storage sections of the solid-state detection elements are read out by scan-driving TFTs connected to the storage sections, and the optical readout method is a method in which the signal charges are read out by irradiating readout light (readout electromagnetic wave) on the solid-state detection elements.
Further, the inventor of the present invention has proposed improved direct conversion solid-state radiation detectors as described, for example, in U.S. Pat. Nos. 6,268,614 and 6,376,857. The improved direct conversion solid-state radiation detectors are direct conversion and optical readout type solid-state radiation detectors. These detectors include the following in the order listed below: a first conductive layer which is transparent to recording radiation; a recording photoconductive layer which shows photoconductivity (more precisely, radiation conductivity) when irradiated by the recording radiation transmitted through the first conductive layer; a charge transport layer acting as substantially an insulator against charges having the same polarity as charges charged on the first conductive layer and as substantially a conductor for charges having the opposite polarity; a readout photoconductive layer which shows photoconductivity (more precisely, electromagnetic wave conductivity) when irradiated by a readout electromagnetic wave; and a second conductive layer which is transparent to the readout magnetic wave. Here, signal charges (latent image charges), representing image information, are stored in the interface (storage sections) between the recording photoconductive layer and charge transport layer.
The image signals outputted from the solid-state radiation image detectors of various types described above are outputted to outside, then subjected to various kinds of signal processing by a signal processing unit in the subsequent stage, and outputted as visible information through an output means such as a CRT, or the like. In this way, the use of the solid-state radiation detector allows image signals representing radiation image of a subject to be obtained and immediately outputted as a visible image or the like.
In the solid-state radiation detector described above, the solid-state radiation detector is connected to a substrate on which a signal detection circuit is provided through a TAB (Tape Automated Bonding) film. As illustrated in FIG. 12, in elements 200, which are linear wires, connection sections 201 for connecting the elements 200 to the TAB are disposed in a line, so that a pitch of the elements 200 is the same as a pitch of the connection sections 201. Here, the pixel density of the detector may be increased by narrowing the pitch of the elements 200. The connection sections 201, however, need to be formed with a greater width than that of the elements 200 for structural reasons, so that elements 200 may not be formed with a narrower pitch than that of the connection sections 201, which has limited the pixel density.